Display panel

ABSTRACT

A display panel includes a plurality of gas-filled cells which comprise apertures in an insulating plate, and each cell has a cathode at its lower end and an anode at its upper end, from which light exits to a viewer. The walls of the cells are made of light-reflecting material so that nonaxial light rays generated at each cathode reflect back and forth upwardly along the cell walls and exit at different angles. With light rays thus exiting at a wide range of angles, an effective wide viewing angle is presented to a viewer. The surface of the apertured plate which faces the viewer is also light-absorbent to minimize light reflection therefrom toward the viewer.

United States Patent Inventor Bernard Caras Princeton, NJ. Appl. No.8,773 Filed Feb. 5, 1970 Patented Nov. 9, 1971 Assignee BurroughsCorporation Detroit, Mich. Continuation-impart of application Ser. No.850,841, Aug. 18, 1969, now abandoned.

DISPLAY PANEL 9 Claims, 13 Drawing Figs.

U.S. C1 313/210, 313/114, 313/220, 313/169 R 1nt. Cl 1-101j 61/30 Fieldof Search 313/109,

109.5,110, 113, 210, 217, 220; 315/169 R, 169 TV [56] References CitedUNITED STATES PATENTS 2,555,749 6/1951 Krefft 313/109 2,216,220 10/1940Baker 313/220 X Primary Examiner-Raymond F. Hossfeld Attorneys-KennethL. Miller and Robert A. Green ABSTRACT: A display panel includes aplurality of gas-filled cells which comprise apertures in an insulatingplate, and each cell has a cathode at its lower end and an anode at itsupper end, from which light exits to a viewer. The walls of the cellsare made of light-reflecting material so that nonaxial light raysgenerated at each cathode reflect back and forth upwardly along the cellwalls and exit at different angles. With light rays thus exiting at awide range of angles, an effective wide viewing angle is presented to aviewer. The surface of the apertured plate which faces the viewer isalso light-absorbent to minimize light reflection therefrom toward theviewer.

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DISPLAY PANEL This application is a continuation-in-part of applicationSer. No. 850,841, filed Aug. 18, 1969, now abandoned.

BACKGROUND OF THE INVENTION Display panels comprising a plurality ofgas-filled cells which can be turned on selectively to display a messageare well known in the an. In a recent development, a display panel hasbeen constructed having an array of gas-filled cells which have glowcathodes at their lower ends and anode electrodes at the upper endsfacing a viewer. These devices have been built and operatedsuccessfully, and they have a satisfactory viewing angle; however, thepresent invention provides still greater viewing angle and opticalefficiency.

SUMMARY OF THE INVENTION Briefly, according to the invention, a displaypanel includes a plurality of light-generating cells whose wallsefficiently utilize light generated at the cathodes regardless of theangle at which it is generated, and the panel has an effective wideviewing angle. In addition, the panel is constructed to have improvedcontrast ratio and optical efficiency.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a displaypanel embodying the invention;

FIG. 2 is an exploded view of the panel of FIG. 1;

FIG. 3 is a sectional view along the lines 33 in FIG. 1;

FIG. 4 is a sectional view along the lines 4-4 in FIG. 1;

FIGS. 5 to 9 show different modification of a portion of the panel ofthe invention;

FIG. 10 is a sectional view of a modification of a portion of theinvention;

FIG. 11 is a sectional view of another modification of a portion of theinvention;

FIG. 12 is a sectional view of another modification tion of theinvention; and

FIG. 13 is a sectional view of a single display cell which illustratesthe effectiveness of the invention in providing a wide viewing angle.

of a por- DESCRIPTION OF THE PREFERRED EMBODIMENTS A display panel 10embodying the invention includes a first insulating plate of glass,ceramic, or the like having a plurality of parallel slots or channelsformed therein and extending from the top surface 40 to close to thebottom surface 50 thereof. For purposes of illustrating and describingthe invention, the panel is oriented so that the slots extendhorizontally. The slots may have any suitable cross section. A V- shapedcross section is shown in FIGS. 2 to 4; however, any other suitablecross section may be employed. For example, a rectangular or squarecross section is shown in FIG. 5, and, in FIGS. 6 and 7, the slot has anarrow upper portion and an enlarged lower portion. In FIG. 8, a slothas a wide upper portion and a narrower lower portion, and in FIG. 9, aslot has a generally inverted V shape.

First electrodes 60 are seated at the bases of the slots, and, since theslots are parallel, so are the electrodes. Electrodes 60 may be wires,flat strips, or they may have any suitable shape, depending on the shapeof the slot. These electrodes might also be plated or evaporated orotherwise formed in the slots. The electrodes 60 might also be securedby a cement such as a glass frit or the like at the ends of slots 30 orat any other suitable location.

The panel also includes second electrodes 70 seated on the top surface40 of the first plate 20. The second electrodes 70 are also parallel toeach other, and they are oriented perpendicular to the first electrodes60. The electrodes 70 are preferably flat strips, and they may also beseated in slots 80 formed in the top surface 40 of the plate 20, asillustrated in FIG. 2, or in slots in the second insulating plate ll0which is disposed above them. The region at which each second electrode70 crosses a first electrode 60 defines a gas cell 90, and eachelectrode 70 has an aperture at this region if it is a flat strip, or itis suitably shaped or offset, or the like to provide a smallcommunication opening from electrode 60 through electrode 70 to otherelements disposed above the electrodes 70 (to be described).

The second insulating plate 110, having a plurality of apertures orcells 120 arrayed in rows and columns, is seated on the top surface ofplate 20, with each aperture or cell aligned with a cell 90 which isdefined by a crossing of a second electrode 70 and a first electrode 60.Each aperture 120 thus comprises a cell which is vertically aligned witha cell 90 formed by the first and second electrodes and the portions ofthe slot 30 between them. The plate may be of any suitable dielectricmaterial such as glass, ceramic, or the like, and the holes or cells maybe cylindrical, or they may have any other suitable shape.

In a preferred construction, the apertures of plate 110 havelight-reflecting walls. This permits nonaxially directed light generatedat a cathode electrode 70 in cells I20 to reflect back and forth andexit at different angles such that the overall viewing angle of thepanel is improved. In addition, the top surface of plate 110 is renderedlight-absorbent by being darkened or blackened or the like to prevent orminimize ambient light reflections. A black glaze or black frit or thelike which will not interfere with panel operation can be used for thispurpose. For this preferred construction, the plate 110 may be made ofmany light-reflecting insulating materials such as alumina, fosterite,steatite, white glass, boron nitride, beryllium oxide, mullite, or Opalglass, all of which provide the desired light-reflectivity in the cells120.

In other embodiments of the invention, the top surface of plate 110 maybe covered with a light-absorbent sheet 190 (FIG. 10) of, for example,black mica, black glass or the like, rather than a light-absorbentcoating. Plate 110 might also be made of a metal sheet 194 coated with afilm 196 of insulating material such as porcelain, glass, or the like(FIG. 11) suitably colored to be light-absorbent. Also, in plate 110,the walls of cells 120 could be coated with a light-reflecting material200 such as chromium or the like, as illustrated in FIG. 12.

Referring now to other features of panel I0, third electrodes are seatedon the upper surface of the apertured plate 110, and they are preferablyembedded either in slots in plate 110 or in a transparent cover plate orviewing plate I50 which is seated on plate 110. The electrodes 130 areoriented parallel to the first electrodes 60, and each is aligned with arow of apertures 120 in the plate 110. The electrodes 130 may also beflat strips or wires or the like, and they are either apertured, or theyare otherwise suitably shaped so that a viewer looking through top platecan look into the cells 120.

In panel 10, the electrodes 60, 70, and 130 may be secured in place bymeans of a suitable cement such as a glass frit (not shown). They mightalso be held in place by a mechanical tight fit in slots or grooves inthe plates which they lie between. In addition, in the completed device,the plates 20, 110, and 130 are sealed together at their edges by meansof a mass of glass frit or the like shown in FIGS. 3 and 4. Forconvenience in making this seal, top plate 150 and bottom plate 20 areusually made somewhat larger than center plate 110, as shown in FIGS. 2and 3. This arrangement is not required, however.

Panel 10 also includes an ionizable gas such as argon, neon, or thelike, or mixtures of gases and a small quantity of mercury, all at asuitable pressure for the intended purpose. The gas may be introduced bymeans of a tubulation (not shown) suitably secured to the panel, or itmay be introduced in any other suitable manner.

The advantage of the invention with respect to improving viewing angleis illustrated schematically in FIG. 13, which shows a typical cell inwhich cell glow appears at the cathode at the base of the cell. Assumingthat there is little or no light reflection from the walls of the cell,the light rays A, which

1. A display panel comprising an envelope including an insulating plate having a plurality of cells arrayed in rows and columns, said cells being filled with a gas capable of sustaining cathode glow, said insulating plate having a top surface and a bottom surface, a cathode electrode associated with each cell and positioned near said bottom surface and an anode electrode associated with each cell and located adjacent to said top surface, said top surface being opaque and light-absorbent, said cells having walls which are light-reflecting so that nonaxially directed light generated adjacent to said cathodes is reflected by the walls of the cells and exits from said cells at said top surface of said plate at such angles that a wide viewing angle for the cells is achieved.
 2. The panel defined in claim 1 wherein said plate is made of a white, light-reflecting material, and said top surface is coated with an opaque, light-absorbent material.
 3. The panel defined in claim 1 wherein said plate is made of a material selected from the group consisting of alumina, fosterite, steatite, whiTe glass, Opal glass, boron nitride, beryllium oxide, and mullite, and said opaque material is a black frit.
 4. A display panel comprising a gas-filled envelope including a plate having a plurality of cell apertures arrayed in rows and columns, said plate having a top surface and a bottom surface, a cathode electrode associated with each cell and positioned near said bottom surface of said plate and an anode electrode associated with each cell and located adjacent to said top surface, said top surface of said plate being generally light-absorbent, said cells having walls which are light-reflecting so that nonaxially directed light rays generated adjacent to said cathodes are reflected by said cell walls and exit from said cells at said top surface of said plate at different angles to that said cells appear to have a wide viewing angle.
 5. The panel defined in claim 4 wherein said plate carries a sheet of light-absorbent material on its top surface.
 6. The panel defined in claim 4 wherein said plate is made of metal and is coated with a layer of light-absorbent insulating material.
 7. The panel defined in claim 4 wherein the walls of said cells carry a light-reflecting coating.
 8. A display panel comprising an envelope including an insulating plate having a plurality of cells filled with a gas capable of sustaining cathode glow, said insulating plate having a top surface and a bottom surface, a cathode electrode and an anode electrode associated with each cell and spaced from each other with one positioned adjacent to said bottom surface and the other positioned adjacent to said top surface, said top surface being opaque and light-absorbent, said cells having walls which are light-reflecting so that nonaxially directed light generated adjacent to said cathodes is reflected by the walls of the cells and exits from said cells at said top surface of said plate at such angles that a wide viewing angle for the cells is achieved.
 9. A display panel comprising a gas-filled envelope including a plate having a plurality of cell apertures arrayed in rows and columns, said plate having a top surface and a bottom surface, a cathode electrode and an anode electrode associated with each cell and spaced from each other with one positioned near said bottom surface of said plate and the other located adjacent to said top surface, said top surface of said plate being generally light-absorbent, said cells having walls which are light-reflecting so that nonaxially directed light rays generated adjacent to said cathodes are reflected by said cell walls and exit from said cells at said top surface of said plate at different angles to that said cells appear to have a wide viewing angle. 